Journal of Applied Crystallography

Volume 32, Part 2 (April 1999)

Cover illustration: Simulated diffraction pattern for a two-dimensionally disordered decasil (porous SiO2) calculated using a fast recursive algorithm. The plane is
perpendicular to c with the reciprocal index l = 1; the error probability is 0.5 and the intensities are scaled to 25% of the highest value. Courtesy of Peter Daniels.

research papers

Influence of miscut on crystal truncation rod scattering

A. Munkholm and S. Brennan

Synopsis:

The effect of miscut on the intensity and direction of X-ray crystal truncation rod (CTR) scattering is presented for both simple cubic and diamond cubic lattices. Data collection schemes are
presented for correctly measuring the CTR intensity of a crystal with miscut.

White-beam topography of Rayleigh waves: a numerical study

V. Mocella and Y. Epelboin

Synopsis:

The contrast of white-beam stroboscopic synchrotron topographs of Rayleigh waves induced by a piezoelectric transducer in an -quartz crystal is analysed. A periodic optimal thickness is found that maximizes the film contrast.

Polycapillary X-ray optics for microdiffraction

C. A. MacDonald, S. M. Owens and W. M. Gibson

Synopsis:

Use of the recently developed polycapillary optics technology to collimate and focus X-ray beams provides significant benefits, including increased signal, high-energy background rejection and
convenience of alignment, for diffraction with spatial resolution of the order of tens of micrometres or from small samples.

Synchrotron radiation topographic observation of KTiOPO4 crystals under an electric field

In situ white-beam synchrotron radiation topographic observations under an electric field have been made on the KTiOPO4 family of
crystals. The quasi-one-dimensional conductivity is a governing factor in the explanation of the field-related phenomena.

P. Dera and A. Katrusiak

Synopsis:

A normal-beam equatorial four-circle diffractometer with no restrictions on its (equivalent to of Eulerian
cradle and to of a cradle), and axes is described. The mathematical formalism eliminates
possible misalignments of the goniometer axes.

B. Weyerich, J. Brunner-Popela and O. Glatter

Synopsis:

The generalized indirect Fourier transformation method is a new technique for the evaluation of small-angle scattering data from semi-dilute or dense systems. In this contribution, the influence
of polydispersity is considered by using an effective structure factor.

Correction of diffraction optics and P-V-T determination using thermoelastic equations of state of
multiple phases

Y. Zhao, R. B. Von Dreele and D. J. Weidner

Synopsis:

A method to determine experimental P-V-T data and to correct misalignment of diffraction optics using thermoelastic equations of state of multiple phases is
presented. This technique is crucial for experiments conducted under the extreme conditions of high pressures, high temperatures and dynamic reactions.

D. Babonneau, A. Naudon, D. Thiaudière and S. Lequien

Synopsis:

The grazing-incidence small-angle X-ray scattering (GISAXS) technique was used to analyse the morphological structure of a C-Ag co-sputtered thin film depending on the depth. A comparison of the
results with those for C/C-Ag and Ag/C thin films is presented.

Crystalline and microstructure study of the AlN-Al2O3 section in the Al-N-O system. I. Polytypes and -AlON spinel phase

P. Tabary and C. Servant

Synopsis:

The crystalline and microstructure of some phases of the pseudobinary AlN-Al2O3 system are discussed, with special attention
to the spinel phase. X-ray and neutron diffraction Rietveld peak-profile refinement data have been employed in the analysis
of different hypotheses of the structures.

Crystalline and microstructure study of the AlN-Al2O3 section in the Al-N-O system. II. '- and -AlON spinel phases

P. Tabary and C Servant

Synopsis:

Results from the crystalline and microstructure study of the ' and -AlON spinel phases by X-ray diffraction, neutron diffraction and standard-resolution transmission electron microscopy techniques are reported. A structural model
is proposed to account for the double modulation of conformation and displacement of the cations and anions for the two phases.

P. W. Stephens

Synopsis:

A model is developed for anisotropic peak broadening in powder diffraction spectra based on the moments of the multi-dimensional distribution of lattice metrics. The technique is illustrated with
two examples: sodium p-hydroxybenzoate and rubidium fulleride.

The dislocation model of strain anisotropy in whole powder-pattern fitting: the case of an Li-Mn cubic spinel

T. Ungár, M. Leoni and P. Scardi

Synopsis:

Anisotropic strain broadening in a cubic Li-Mn spinel has been interpreted by the dislocation model of the mean-square strain. Combination of this dislocation model with the Fourier coefficients
method enabled excellent whole powder-pattern fitting.

Diffuse X-ray scattering by 2,3-dimethylnaphthalene

R. Schreier and J. Kalus

Synopsis:

The diffuse intensity distribution of X-rays scattered from a dipolarly disordered single crystal of 2,3-dimethylnaphthalene has been measured. Correlation coefficients characterizing the mean
mutual orientation of neighbouring molecules were determined.

A procedure for separating the inelastic and elastic contributions to the total scattering in high-energy scattering experiments is described. The procedure uses curve fitting of energy-dispersive
X-ray spectra and is applied to scattering from amorphous silicon.

Online 1 April 1999

teaching and education in crystallography

Crystallographic CourseWare

M. E. Kastner

Synopsis:

The software described uses animations and interactive programs to teach crystal growth, plane- and space-group symmetry elements, unit cells and asymmetric units, reciprocal space, precession
photographs and an introduction to reading the International Tables for Crystallography.

Online 1 April 1999

short communications

Automatic determination of diffuse-peak positions and the centre of a diffraction pattern

S. J. Wilkinson and D. W. L. Hukins

Synopsis:

Correlation, with a two-dimensional Gaussian function, was used to locate the positions of diffuse peaks in X-ray diffraction patterns of oriented collagen. The centre of each pattern was found by
convolution with a two-dimensional Gaussian function.

AXES1.9: new tools for estimation of crystallite size and shape by Williamson-Hall analysis

H. Mändar, J. Felsche, V. Mikli and T. Vajakas

Synopsis:

Complicated analyses of X-ray powder diffraction peak shape on the bases of peak fitting, the Voigt method and the Williamson-Hall plot are implemented in the form of user-friendly dialogues into
an MS-DOS program. The tools are used for the estimation of apparent (X-ray) crystallite size and lattice strain, as well as the calculation of actual dimensions of crystallites, assuming spherical
or cylindrical shape.

MESO - a program to convert X-ray diffraction data from angular to reciprocal space

K. R. Locherer, A. Buckley and E. K. H. Salje

Synopsis:

A program has been written to convert X-ray diffraction data, generated by Siemens and INEL detectors, to reciprocal space. The application of the program to diffuse scattering in Al-doped YBCO
superconductor and WO3 is presented.

FINDNCS: a program to detect non-crystallographic symmetries in protein crystals from heavy-atom sites

G. Lu

Synopsis:

A computer program to detect non-crystallographic symmetry in protein crystals from heavy-atom sites is presented. The program has been successfully applied in the determination of at least eight
protein structures.

laboratory notes

A. H. Nahlé, F. C. Walsh, C. Brennan and K. J. Roberts

Synopsis:

The design of in situ electrochemical cells for X-ray absorption and diffraction studies requires attention to the window material. X-ray absorption values are
calculated for a range of common polymer window materials.